JP3655625B1 - Process for producing an aliphatic polyester blown film - Google Patents

Abstract

The present invention provides a method for producing an aliphatic polyester inflation film capable of stably producing a long tubular film of aliphatic polyester having biodegradability.
In a method for producing an aliphatic polyester blown film, linear low-density polyethylene or 90-100% by weight of low-density polyethylene and 0-10% by weight of aliphatic polyester are supplied to an extruder to start film formation. The resin supplied to the extruder was switched to a linear low density polyethylene or a mixture of 20-80% by weight of low density polyethylene and 20-80% by weight of aliphatic polyester, and after film formation was continued, only the aliphatic polyester was extruded. A method for producing an aliphatic polyester inflation film, characterized in that the film is supplied to a machine to form a film.
[Selection] Figure 1

Description

  The present invention relates to a method for producing an aliphatic polyester blown film. More specifically, the present invention relates to a method for producing an aliphatic polyester inflation film capable of stably producing a long tubular film of biodegradable aliphatic polyester.

In recent years, aliphatic polyester has attracted attention as a biodegradable plastic material. Plastic films have good film forming properties and processability, and are widely used as packaging materials. However, many plastic films have problems in treatment after use, such as a large amount of heat generated during combustion, which damages the incinerator and is not suitable for landfill because it is bulky and does not decompose in the soil. On the other hand, aliphatic polyesters are suitable for landfill treatment because they generate less heat when burned than polyolefins and are less likely to damage the incinerator and decompose by the action of microorganisms in the natural environment.
As a method for producing a plastic film used as a packaging material, an inflation film forming method is widely used. Inflation film molding is a method in which molten resin kneaded in an extruder is extruded into a cylindrical shape from an annular die, and a certain amount of air is put into the cylindrical molten film to pressurize and expand to form bubbles. After that, it is cooled and solidified to continuously obtain a tubular film. The inflation film forming method has lower equipment costs compared to the T-die method, the dimensions can be changed depending on the expansion method, a long tubular film can be obtained, and the bag can be easily processed by secondary processing. Since it can be made into a body, it is suitable for the production of a plastic film as a packaging material.
As the resin used for the inflation film molding method, polyolefin resins such as linear low density polyethylene, low density polyethylene, high density polyethylene, ethylene vinyl acetate copolymer, and polypropylene are generally used. The present inventors examined the production of aliphatic polyester by an inflation film molding method in consideration of application of biodegradable aliphatic polyester to packaging materials. However, since the aliphatic polyester has a lower melt tension than the polyolefin resin, the bubble shape tends to fluctuate, and it has been difficult to stably produce a high-quality film.
As a method for producing a foamed defibrated body of an aliphatic polyester capable of performing inflation molding with high productivity, a composition containing an aliphatic polyester and a foaming agent is formed into a foamed film by an inflation method, and the foamed film is used as a guide member. In the method including the step of expanding and defibrating while being contacted, a method for producing a foamed defibrated body of an aliphatic polyester in which the critical surface tension of the material constituting the surface of the guide member is 15 to 65 dyne / cm is proposed. (Patent Document 1). However, when this method is applied to the production of an aliphatic polyester blown film, not only the apparatus becomes complicated, but the characteristics of the blown film forming method that the dimensions of the film can be changed by the way the bubbles are expanded. It will be lost.
JP-A-8-325918 (2nd page, FIG. 1)

  An object of the present invention is to provide a method for producing an aliphatic polyester inflation film that can stably produce a long tubular film of aliphatic polyester having biodegradability.

As a result of intensive studies to solve the above-mentioned problems, the present inventors started to form a film by supplying linear low density polyethylene or low density polyethylene to the extruder, and the resin to be supplied to the extruder After switching to a low-density polyethylene or a mixture of low-density polyethylene and aliphatic polyester and continuing the film formation, by supplying only the aliphatic polyester to the extruder and forming the film, the fluctuation of the bubble shape is prevented, The inventors have found that it is possible to stably produce an aliphatic polyester blown film, and have completed the present invention based on this finding.
That is, the present invention
(1) In the method for producing an aliphatic polyester inflation film, linear low-density polyethylene or low-density polyethylene 90 to 100% by weight and aliphatic polyester 0 to 10% by weight are supplied to an extruder to start film formation, The resin supplied to the extruder is switched to a linear low density polyethylene or a mixture of 20 to 80% by weight of low density polyethylene and 20 to 80% by weight of aliphatic polyester, and after film formation is continued, only the aliphatic polyester is extruded. A method for producing an aliphatic polyester inflation film, wherein
(2) Switching to linear low-density polyethylene or a mixture of 20-80% by weight of low-density polyethylene and 20-80% by weight of aliphatic polyester is performed a plurality of times, and the content of aliphatic polyester in the mixture is successively increased. (1) A method for producing an aliphatic polyester inflation film according to (1), and
(3) The method for producing an aliphatic polyester inflation film according to (1), wherein the aliphatic polyester is polybutylene succinate or polybutylene succinate adipate,
Is to provide.
Furthermore, as a preferred embodiment of the present invention,
(4) The method for producing an aliphatic polyester inflation film according to (1), wherein linear low density polyethylene is supplied to an extruder and film formation is started.
Can be mentioned.

  According to the method of the present invention, it is possible to prevent a change in the shape of a bubble of an aliphatic polyester having a low melt tension and to stably produce a high-quality aliphatic polyester inflation film.

In the method for producing an aliphatic polyester blown film of the present invention, 90 to 100% by weight of linear low density polyethylene (LLDPE) or low density polyethylene (LDPE) and 0 to 10% by weight of aliphatic polyester are supplied to an extruder. After starting film formation and switching the resin supplied to the extruder to linear low density polyethylene or a mixture of low density polyethylene 20 to 80% by weight and aliphatic polyester 20 to 80% by weight, the film formation is continued. Only aliphatic polyester is supplied to the extruder to form a film.
When aliphatic polyester is supplied to the extruder from the beginning of film formation, the shape of the bubble formed by inflating the air by inserting air into the cylindrical film of the molten resin extruded from the annular die in a cylindrical shape is easy to change, and high quality It is difficult to stably produce the inflation film. After the linear low density polyethylene or low density polyethylene is supplied to the extruder and film formation is started to form bubbles with a stable shape, the resin supplied to the extruder is made of linear low density polyethylene or low density polyethylene and fat. By switching to a mixture with an aliphatic polyester, film formation is continued, and only aliphatic polyester is supplied to the extruder to form a film, thereby preventing bubble shape fluctuations and producing a high-quality aliphatic polyester inflation film. It becomes possible to manufacture stably.

In the method of the present invention, the resin supplied when starting film formation is linear low density polyethylene or low density polyethylene, or a mixture of 90% by weight or more of these polyethylenes and 10% by weight or less of aliphatic polyesters. When the proportion of the aliphatic polyester in the linear low density polyethylene or the mixture of the low density polyethylene and the aliphatic polyester exceeds 10% by weight, the shape of the bubble at the start of film formation tends to fluctuate, and the film is stably formed. May be difficult.
In the method of the present invention, it is preferable to start the film formation by supplying linear low density polyethylene or low density polyethylene to the extruder, and starting the film formation by supplying linear low density polyethylene to the extruder. More preferred. Linear low-density polyethylene forms a stable bubble with little shape fluctuation, and the bubble supply when the resin supplied to the extruder is switched from linear low-density polyethylene to a mixture of linear low-density polyethylene and aliphatic polyester. Little change in shape.

In the method of the present invention, linear low-density polyethylene or low-density polyethylene 90 to 100% by weight and aliphatic polyester 0 to 10% by weight are supplied to the extruder and film formation is started. The film formation is continued by switching to a mixture of 20 to 80% by weight of linear low density polyethylene and 20 to 80% by weight of aliphatic polyester. As the resin to be switched, linear low density polyethylene or a mixture of 80 to 90% by weight of low density polyethylene and 10 to 20% by weight of aliphatic polyester, linear low density polyethylene or 1 to 20% by weight of low density polyethylene and aliphatic polyester Although it is possible to use a mixture of 20 to 99% by weight, the resin supplied to the extruder can be switched to only the aliphatic polyester without usually using a resin mixture having this composition range.
In the method of the present invention, switching to a mixture of linear low-density polyethylene or 20-80% by weight of low-density polyethylene and 20-80% by weight of aliphatic polyester is performed a plurality of times, and the content of aliphatic polyester in the mixture is adjusted. It is preferable to increase sequentially. By switching the resin mixture a plurality of times and sequentially increasing the content of the aliphatic polyester in the resin mixture, fluctuations in the shape of the bubbles can be suppressed and inflation molding can be continued stably. There are no particular restrictions on the number of times the resin mixture is switched, but normally only 2 to 3 times of switching can be used to supply only the aliphatic polyester to the extruder, producing a stable, high-quality aliphatic polyester inflation film. can do.

The aliphatic polyester used in the method of the present invention is not particularly limited. For example, polyethylene succinate, polyethylene succinate adipate, polybutylene succinate, polybutylene succinate adipate, polylactic acid, poly-γ-butyrolactone, poly-δ-valero Examples thereof include lactones, poly-ε-caprolactone, copolymers of these aliphatic polyesters, and compounds obtained by reacting terminal hydroxyl groups of these aliphatic polyesters with diisocyanate compounds to extend the chain. Among these, polybutylene succinate and polybutylene succinate adipate can be particularly preferably used since they have good inflation moldability and biodegradability.
There is no restriction | limiting in particular in the linear low density polyethylene used for this invention method, For example, an ethylene-butene copolymer, an ethylene-hexene copolymer, an ethylene-octene copolymer etc. can be mentioned. The melt flow rate of the linear low density polyethylene or low density polyethylene used in the method of the present invention is not particularly limited, but the melt flow rate measured at a temperature of 190 ° C. and a load of 21.18 N is 0.1 to 3.7 g / 10 min. It is preferable that it is 0.5 to 2.5 g / 10 min.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
An inflation film was produced using an aliphatic polyester [Showa Polymer Co., Ltd., Bionore 5151, melt flow rate 1.7 g / 10 min (190 ° C., 21.18 N)].
FIG. 1 is a schematic view of the apparatus used. The screw diameter was 45 mm, the diameter of the annular die was 100 mm, and the lip gap was adjusted to 1.5 mm. The temperature of A under the hopper 1 is set to 135 to 140 ° C., the temperatures of B and C of the screw 2 are set to 150 to 155 ° C., the temperatures of D and E of the annular die 3 are set to 145 to 150 ° C., and the expansion ratio is 3.5. As a double, a tubular film having a folding diameter of 550 mm and a thickness of 30 μm was formed.
When 10 kg of linear low density polyethylene [melt flow rate 2.0 g / 10 min (190 ° C., 21.18 N)] is put into a hopper to form a film and the resin in the hopper is almost gone, 7 kg of linear low density polyethylene A mixture of 3 kg of aliphatic polyester and 3 kg of aliphatic polyester was put into the hopper to continue film formation. When almost no resin was left in the hopper, a mixture of 6 kg of linear low density polyethylene and 4 kg of aliphatic polyester was put into the hopper. When the membrane was continued and the resin in the hopper was almost exhausted, the aliphatic polyester was put into the hopper to form an aliphatic polyester inflation film. When the resin was switched from linear low density polyethylene to a mixture of 7 kg of linear low density polyethylene and 3 kg of aliphatic polyester, the bubble shape was slightly distorted, but it immediately returned to a stable shape, and thereafter stable. A film could be formed.
The obtained aliphatic polyester blown film was subjected to a tensile test according to JIS Z 1702 7.5 and a heat seal strength test according to JIS Z 1711 8.4. The tensile strength in the longitudinal direction was 63.4 MPa and the elongation was 360%, and the tensile strength in the transverse direction was 61.9 MPa and the elongation was 820%. The heat-seal test piece is made by stacking two 200 mm × 200 mm inflation films and heat-sealing at a temperature of 175 ° C., a pressure of 220 kPa, and a sealing time of 0.3 seconds using a 2 mm × 200 mm seal bar, and the width of the seal portion is 10 mm. It was made by punching out dumbbells. The heat seal strength was 12N.
The tensile strength of the type B film specified in JIS Z 1702 “Polyethylene film for packaging” is 29.4 MPa or more and the elongation is 150% or more. In addition, both the elongation and the quality are more than twice this standard. In addition, the heat seal strength of the film of type B, nominal thickness 0.03 mm specified in JIS Z 1711 “polyethylene film bag” is 11.77 N or more when the width of the test piece is 15 mm. The resulting aliphatic polyester blown film also exceeds this level in heat seal strength.

  According to the method for producing an aliphatic polyester inflation film of the present invention, a long tubular film of aliphatic polyester having biodegradability can be produced stably. The aliphatic polyester blown film produced by the method of the present invention satisfies all the tensile strength, elongation and heat seal strength required for packaging materials. Aliphatic polyester having biodegradability is decomposed by microorganisms even when buried in the soil, and eventually becomes water and carbon dioxide, so that it can be disposed of without destroying the global environment.

It is the schematic of the apparatus used in the Example.

Explanation of symbols

1 Hopper 2 Screw 3 Ring die

Claims (3)

  In the production method of an aliphatic polyester blown film, linear low-density polyethylene or low-density polyethylene 90 to 100% by weight and aliphatic polyester 0 to 10% by weight are supplied to an extruder to start film formation. The resin to be supplied is switched to linear low density polyethylene or a mixture of 20 to 80% by weight of low density polyethylene and 20 to 80% by weight of aliphatic polyester, and after film formation is continued, only aliphatic polyester is supplied to the extruder. A method for producing an aliphatic polyester inflation film, characterized by comprising:   2. A linear low density polyethylene or a mixture of 20 to 80% by weight of low density polyethylene and a mixture of 20 to 80% by weight of aliphatic polyester is switched a plurality of times, and the content of aliphatic polyester in the mixture is successively increased. A process for producing an aliphatic polyester inflation film as described.   The method for producing an aliphatic polyester inflation film according to claim 1, wherein the aliphatic polyester is polybutylene succinate or polybutylene succinate adipate.

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